Tubular electric grounding rod



' Jan. 31, 1939.

G. A. HORNBECKER TUBULAR ELECTRIC GROUNDING ROD Filed March 12, 1958 'earye A/hmbec/m I Patented Jan. 31, 1939 UNITED STATES PATENT OFFICE TUBULAR ELECTRIC GROUNDING ROD Application March 12,

9 Claims.

The present invention relates to an improvement in tubular electrical grounding-rods of a type commonly employed for grounding electrical installations of various kinds to considerable 6 depths in the ground and has for its general object to provide an improved construction and arrangement of parts in devices of this character whereby the high electrical conductivities of copper and other soft metals or alloys can be utilized without rendering the grounding-rods too heavy to be conveniently handled by an individual; too expensive to make for general use; or, otherwise, structurally-incompetent to stand up under the mechanical difficulties which beset the driving of grounding-rods in hard and stony ground.

One object of the invention is to provide an improved construction for grounding-rods on i.- prising an outer relatively thin-walled tubular member constructed of material having high electrical conductivity and an inner core or re enforcement of relatively light, strong, and mechanically-resistant materials organized with and forming a permanent part of the grounding-rod.

Another object of the invention is to provide an improved construction for grounding-rods comprising a tubular outer shell of high electrical conductivity which adds little expense to the manufacture of the grounding-rods and an inner core or filler medium which need not involve any considerable expense to impart the necessary strength to the outer shell of light weight.

Another object of the invention is to provide an improved construction for electrical grounding-rods comprising an outer shell constructed of relatively soft metal of high electrical conductivity and an inner filler-medium which is capable of being axially compressed or condensed and thereby expanded in cross-sectional area to form a consolidated core or reenforcement for the soft outer shell, said core or reenforcement being preferably resilient; capable of receiving the recurring impacts of a driving-rod or ham mer; and serviceable as an impact-transmitting member interposed between said driving-rod and a leading-point which pilots the grounding-rod into the ground.

A iurther object of the invention is to provide a core or reeniorcement of the character referred to, which is organized with and forms a permanent part of the grounding-rod in such a way that it is structurally-competent to counteract the mechanical effects of torsion, flexing, warping, etc., on the exterior wall of the outer shell 1938, Serial No. 195,454

of relatively-soft metal due to driving the grounding-rod in hard or otherwise difiicult ground.

A specific object of the invention is to provide, as an article of manufacture, a groundingrod of inexpensive construction suitable for general use with various kinds of electrical installations to provide a high degree of electrical conductivity, a wide area of contact with the ground in which it is driven; and a structural selfcompetency to enable it to be driven in ground where the surrounding conditions are unfavorable.

With the above and other objects in View as will appear to those skilled in the art from the present disclosure, this invention includes all features in the said disclosure which are novel over the prior art.

In the accompanying drawing:

Fig. 1 is a small-scale view in vertical elevation of a completed installation of a grounding-rod constructed in accordance with the principles of the present invention;

Fig, 2 is a View in vertical elevation of one section of the filler medium removed from the driving-rod according to the form of this device shown on the drawing;

Fig. 3 is an enlarged vertical section of the assembled parts above ground and prior to the beginning of the driving operation, the drivinghammer being shown in position at the top; parts being broken away and parts shown in elevation;

Fig. 4 is a vertical section similar to Fig. 3 showing the relative arrangement of the parts at the conclusion of the driving operation;

Fig. 5 is a transverse section on the line 55 of Fig. 4 taken from below; and

Fig. 6 is a vertical elevation of the completed installation before the wiring connection has been made, portions being broken away.

According to the embodiment of the invention shown on the drawing, a tubular grounding-rod it which is preferably constructed of thin-walled hard-drawn copper tubing, carries a leadingpoint i i which is rigidly attached thereto at the bottom. The tubular member HI may vary greatly with respect to length, diameter and wallthickness, depending upon local conditions surrounding any particular installation. Thus, for example, the tubular member may vary in length from about two feet to eight or more feet and may vary in external diameter from about onehalf inch to about one and one-quarter inch. The wall-thickness of said tube-member is preferably within the range of .025 inch to .035 inch approximately, for the purpose of providing maximum surface area for contact with the ground and at the same time minimizing the amount of copper, or other metal required for a given installation.

The leading-point H may be made of iron and usually is provided with a conical head as shown on the drawing and has an axial shank I3, which is suitably proportioned to be inserted into the lower end of the tubular member It with a driving-fit. For this purpose, the outside diameter of the shank l3 may be made .005 inch larger than the internal diameter of the tubular member LE3. At its largest diameter, the conical point is formed with an annular abutment M which engages the lower end of the copper tube IE1 and under certain conditions receives the driving impacts delivered thereto by said tube after the filler-medium has been consolidated within the tubular member I0 during an earlier stage of the driving operation.

A driving operation is facilitated by making the leading-point l l at shoulder M of sufiicient size to provide suitable clearance for the grounding-rod and thus to minimize the frictional resistance thereon during its downward movement into the ground. According to the form of the invention illustrated on the drawing, the core or reinforcement is composed of a filler-medium comprising a plurality of superposed sections it embodied in and forming a part of the complete grounding-rod assembly. These filler-sections may be composed of any suitable material for carrying out the purposes of the present invention. Preferably, the material of which they are made should have a sufficient degree of resilience to effectively support the tubular walls of the driving-rod and for this purpose are preferably made axially compressible and expansible in cross-sectional area into substantially rigid engagement with the inner wall of the tube. For this purpose, a convenient form of filler-medium may be had by the use of a plurality of sections of hard wood, such as the dowel stick shown in Fig. 2, said sections being arranged end to end in the tube and terminating short of the upper end of the tube as shown in Figs. 3 and 4. After the tubular member Ill has been thus partly filled, they maybe axially compressed or condensed before distribution to the trade, or may be driven in the form shown. For this purpose, a driving-tool of the character shown, described and claimed in the co-pending application of Harold C. Daniels, Serial No. 195,323, filed Mar. 11, 1938 may be employed. As shown in Figs. 3 and 4 of the drawing, this driving-tool comprises a relatively-heavy cylindrical hammerhead I'l' providing a hand-grip and a centrallyarranged driving-rod it with its upper end socketed in the hammer-head H with a driving-fit. An annular recess 59 which is formed in the hammer-head i'l around the upper end of driving-rod !8, provides a shoulder 28 which, during the driving operation, may or may not come into hammering engagement with the upper end of tube Iii. Whenever such hammering engagement takes place, it will be seen that the upper end of the tubular shell I Q is effectively supported around its inner and outer circular walls by the upper end of rod I8 and a circular skirt or flange 2! which depends from the hammer-head I]. In driving the grounding-rods described above, a workman supported in any suitable manner a short distance above the ground, presses the leading-point ll into the ground and manipulates the hammer-head ll of drivingrod [8. As the hammering operation continues, the bottom-end of the lowermost section [6 of the filler-medium becomes mushroomed over and about the anvil [5 at the upper end of shank l3 of the leading-point i i, the filler-medium or rod being so designed in diameter and length that it counteracts, by its reenforcement of the tubular wall of shell Iii from within, the bending, torsional and mutilating effects of the ground on its outer surface. By the time the grounding-rod has been driven home in the ground, the fillermedium has become condensed under the recurring impacts of driving-rod it into a consolidated core which fills the shell it from the lower end of the hammer-rod It to the anvil H5 at the top of shank iii of the leading-point H. In this way, the core or reinforcement 'is rendered harder, denser, and more resilient in proportion to the resistance oifered by the ground through which it is driven. In most cases, the grounding-rod can be completely driven before the shoulder 2!? begins to strike upon the upper end of tube iilbut it is readily seen that in the event that the ground in which the driving is being done is unusually resistant or dense, the driving operation can be continued by causing the shoulder 2!] to deliver repeated blows to the upper end of tube 16, which has now become solidly reinforced at the lower end while the upper unfilled end there is effectively supported within and without by driving-rod l8 and skirt 2| to prevent deformation, distortion or mutilation of the tubing IE3. It will be seen, furthermore, that as the driving operation proceeds, the tubular outer wall it of the ground-rod is drawn downwardly not only by the leading-point El which is connected thereto by a driving fit between shank l3 and the inner wall of tube Hi, but also by an increasing frictional grip exerted by the core or reenforcement as it is consolidated within the tubular shell l0.

After the grounding-rod has been driven to the desired depth, the hammer ll with its driving-rod It is removed from tubular shell Ill after which a grounding-clamp 22 is secured to the upper end of the ground-rod to accommodate a ground-wire 23 leading thereto, as shown in Fi 1.

Preferably, the hammer-head IT is formed of suitably-heat-treated tool steel, so that when circumstances require, its upper end may be struck with a sledge to force the grounding-rod through refractory or highly-resistant ground.

In the event that an installation is to be made in extremely refractory or resistant ground, the invention may be readily adapted to this purpose by making the filler-section it of some hard, resistant and preferably resilient material, such as steel. In this case, successive lengths of steel substantially filling the interior bore of the tubing Iii are superposed one above the other to an elevation at which it will be subject to the impact of the driving-shank I8. In this case, while the core or filler is not subject to any considerable axial compression, the pressure of the ground on the exterior wall of tubular shell 10, presses it into strong frictional engagement with the core or filler in such a way as to impel the tube l9 downwardly with the leading-point H and core It.

The invention may be carried out in other specific ways than those herein set forth, without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

I claim:

1. An electrical grounding-rod, comprising: a thin-walled tubular shell formed of material having a high degree of electrical conductivity; a leading-point attached to the lower end of said tubular shell; and a resilient filler-mediurn sub stantially filling said tubular shell to within a predetermined distance of the top thereof to form a driving-socket; said filler-medium being expansible in cross-sectional area under driving impacts thereon to apply pressure to the inner Wall of said tubular shell to counteract the external pressure on said tubular shell.

2. An electrical grounding-rod, comprising: an outer tube of metal having high electrical conductivity; a leading-point attached to the lower end of said tube; and a wood-filler disposed within and expanded under axial pressure into permanent supporting engagement with the inner wall of said tube.

3. An electrical grounding-rod, comprising: an outer tube of metal of high electrical conductivity; a leading-point attached to the lower end of said tube; and a resilient filler-medium substantially filling the interior of said tube from the leading-point to within a predetermined distance of its upper end to provide a drivingsocket at the top, said filler-medium being expansible in transverse cross-section to increase its frictional grip on the inner wall of said tube under recurring impacts transmitted thereby to said leading-point.

4. An electrical grounding-rod, comprising: a tubular conductor of high electrical conductivity; a leading-point having a shank inserted into the lower end of said tubular conductor; and a fillercore of wood having a cross-sectional area substantially the same as that of the interior wall of said tubular conductor, said core of wood being compressible axially and expansible in cross-sectional area under pressure applied to the upper end of said core.

5. The method of making electrical groundingrods, consisting in: forming a tubular conductor having structurally-incompetent walls; introducing a filler-medium into said tubular conductor and subjecting the filler-medium to axial pressure whereby it is expanded in cross-section into supporting engagement with the inner wall of said tube to form a permanent part of the grounding-rod.

6. The method of making grounding-rods, consisting in: forming a tubular shell of metal having a relatively-high electrical conductivity; in closing one end of the tubular shell with a leading-point; placing within the tubular shell a core of wood having a cross-sectional area substantially the same as that of the inner surface of said tubular shell; and in axially compressing the wood core to expand it in crosssectional area into rigid engagement with the inner wall of the tubular shell.

'7. An electrical grounding-rod comprising an outer tubular wall of hard-drawn copper; a leading-point provided with a shank closing the lower end of said tubular wall; and an anvil core substantially filling said tubular wall except for a predetermined length thereof at the top to form a driving-socket within and at the upper end of said tubular well, said core being in expansible engagement with the inner surface of the tubular wall under the impacts of a driving instrument operating thereon within said socket at the upper end of said tubular wall.

8. An electrical grounding-rod, comprising: an outer tubular member constructed of non-ferrous metal having a predetermined diameter suilicient to provide a required electro-conductive capacity and a wall-thickness insufficient to render it structurally self-competent under a driving operation; a leading-point on the lower end of the said outer tubular member; and a filler-medium disposed within and terminating short of the upper end of the said outer tubular member, the said filler-medium being condensible under an axially-applied pressure to provide a consolidated reenforcement in supportable engagement with the inner wall of the said outer tubular member to render the grounding-rod structurally self-competent during a driving operation performed thereon.

9. An electrical grounding-rod, comprising: an outer tubular member constructed of non-ferrous metal having a predetermined diameter sufficient to provide a required electro-conductive capacity and a wall-thickness insufiicient to render it structurally self-competent under a driving operation; a leading-point on the lower end of the said outer tubular member; and a filler-medium disposed within and terminating short of the upper end of the said outer tubular member to form a driving-rod socket, said filler-medium comprising one or more filler-rods expansible in transverse cross-section under recurring impacts of a reciprocatory rod operating within the said socket to rigidly engage the inner wall of the said outer tubular member and thus to render the said tubular-member structurally self-competent.

GEORGE A. HORNBECKER. 

